Screw fastener



Oct. 11, 1949. R. K. F. BAUMLE 2,484,645

SCREW FASTENER Filed oct. 25, 194e Patented Oct. 11, 1949 'SCREW FASTENER uRudolf 3K. "Baumle, Chicago, i111., iassignor -.to :Illinois Tool Works, Chicago, Ill., a corporation of. Illinois Application' October 23, 1946,@'Seilllo705g19'7 2' Claims.

TThis inventionf relates fgenerallyfto selfflccking for lself-sealing lscrews designed "for -use in -fcon- 'ventionally tapped Chelles, and "more 'particularly to screws which fdeperfd vffor 'their ylocking and V'#sealing characteristics upon aggressive iimpinge- -mentfwith the complementarythread convolu- Vtions-in the work.

PScrewfs have .heretofore floeen used which, vare designed specically '-to llockingl-y limpinge ithe crown portions of the complementary thread 1in ythehwork Lpiece. ".'Inthisconnection reference is I@made to Athe Epricr Vpatent -o'f 0.41. lPoupitch, No.

' 222695476, Wherein'the`r0ot Vdiameter of' 'the locking' se'ctionof 'aiscrew1.is-increase'd above-'theinormal root diameter zso fas to 'cause aggressive thread .impingement vwhen the fscr'ew `:is :turned 'within a conventionally :tapped'zhole tin .a work Ipiece. '.Thefprese'nt inventioniis .ooncernedtwith .a 'screw Awhich Snot Ionlylocking'ly impngesrand sealingly .engages -the `crown of the thread :in

tithe work, .but which also isfdesigneditolloclringly and Vfsealin'gly.'.impinge the fsideifaces of the :com-

plementarythread:convolutionsliof.the"work. :In

. other wordsgitissan .object of 'lthfe present vinveny'tion to provide .1i-'a screw of `.the :type 'referred to :abovelwhich isa'diapted 'toieectrcomplete sealing nlbetwe'enftl'ie screw :and the :work along .the 'complementary ithreadrconvolutions thereof.

- More specifically, the invention l'conteinpla'tes A'a self-"locking ior self-*sealing screwf-as set forth above, equipped with fa normal fleading :section and La locking fsection, Fthe thread sconvolutions "o which -are=so :arranged "as ftorensuref v'aggressive 4locking impingementalong the lside'lilace'sfoficcmn Ap'lernentary thread -i convolutions -rina worklpiece.

The present invention contemplates as'crewfiin :which ai holding portion is Iprovided with xmeans along the thread convolutionsthereof to provide "locking and/sealing 'engagementfbetween the lside Zi aces vv'ol said convoluti'onsf'with the f complementary LAside-faces of fthe threaidrn the work.

Itis a further 'object of jthe present yinvention "to xprovide a screw as outlined-above wher'intthe ease with which viprotuloeranl'zes valong gthe moet portion 4are moved into impingement with the threa'dr'in the vworkis"grea"tly Ifacilitated, andi-to v A 2, shown-fin Figure `1to1-incre clearly illustrate the fcircumferentially 'spaced thread engaging vprotuiheranoes; l

.':Figlner y,is a'xtransverse sectional View taken 5 ll:s ulostantially .along .the `line 3*;3 4of Figure 2; @Figure ellis-ian enlarged fragmentary sectional view vof the complementary threadconvolutions yif the work :and screw, saidl section being ytaken :longitudinally-of the screw.;

lFigure 5 :isfarpenspective -view illustrating the -manner in which the {protuberances `and thread convolutions may be 4 producedl contemporaneousdy iby rolling:a .screw blank between .die blocks; ,and ,5 rFigure 6isfenlargedfraginentary View of the workingfface Eof` onevoffthedie blocks rto illus- .trate those portions of A.the-.block which extrude the .circumferentially,fspaced .protuberances on the `thread convolutions ofthe screw.

Referring Inow .to vfthe drawing, whereinlike numerals have Abeen employedlto ydesignate similar lparts throughout the various figures, it `will be 'seenthat one einbo'diinen't of the present invention 'isvshown'ln association with a screw or .'Sbolt .designated generally "bythe numeral 'Hl in '1.35 JvThis lhlding portion jZ2 :might also be `referred to 1as the locking'orsealingportion-of *the screw-ias `'will vloernoredeadilyunderstood-from the f descrip "tionfwhi'chfllows,

The :entering portion 2t of the screw may-he '40 "of fncrm-'al configuration, both in shape 'and 'f size. That ifs fto'fsay,fthe' "thr'ead 'convolutions "on the leadingportion Ill-conform with normal 'thread standards-as distinguished-from the threadv con- 'lvlutions @included 'within the .holding or `flocking 4S-portion 222. 'This lockingfsection "2 is provided "with a plurality df oircuniferentially spaced pro- "tuberancesidesignated generallyvby the numeral y321i. Each :protuberance y.-'cornprises three parts, iname'iw fa part' positioned adjacent the root .of -'fth'e thread .fl which `zwill .hereinafter Ibe .referred i-ito ias the Stoet-'partire 1.and :parts :extending .out- "wardly Sfro'rn opposite sides i of reach: root part 726 .atongitheii-side :faces :or :surfaces of the lthread lconimiiution, thereinafterreferred .to 'as side Apro- "55 z-tuberancerparts 8.

:Attentionf-is directed fto the fact that the `=root `@protubera-'nce vfpafrts f2.6, as vr`shown .in Figure 3, -rise gradually :from vthe -root of the thread to-a Arhighfpo'intcthisigraduallyfrising portion .being in,-

eodicatedby' theletterfA. The :parts 128of thegpro- .Y

tuberances 24 form a continuation of the crest portion of the surface A and extend outwardly beyond thev crest of the threads I6. Thus, as viewed in axial crossv section, the protuberances provide a series of connected U-shaped ribs which extend radially beyond the normal diameterof the screw threads i6. Stating it another way, these protuberances project radially beyond the normal diameter of the root, crest and side surfaces of the thread convolutions. l

The disposition of the protuberances 24 is such that as the holding portiong22 of the screw is turned into association with the threaded aperture of the work piece I8, the crest, root and side surfaces of the thread convolutions of the work are aggressively contacted by said protuberances. After the screw has been i'lnally driven home, the holding portion of the screw is rmly secured against unauthorized-loosening due to the impingement of the protuberances with the thread of the present invention therefore lends itself to applications where it is not only desirable to secure the screw against loosening, but also to prevent leakage of fluid, such as oil and the like, along the thread convolutions. An example of an environment in which a screw of the present invention would provide a practical solution to the problem of oil leakage is found in oil pans secured beneath the enginesof automobiles. This is only one of numerous examples where a self-locking screw, as well as a self-sealing screw, is of practical signicance.

The manner in which the above described protuberances 2li lockingly and sealingly engage complementary thread convolutions in the work is clearly illustrated in Figure 4. This figure constitutes an enlarged axial sectional view of the mating convolutions in the screw and work. The above described protuberances may be economically provided in a screw body by the use of thread rolling dies and 32, as illustrated in Figure 5.

Longitudinal serrations or teeth 34 yin the die blocks cause the thread I6 to be rolled in a screw blank lila. This has been the conventional method of producing screw threads for many years.. At spaced intervals 36 along the die block 30 the serrations 34 are interrupted with congurations which, as the screw blank isvrolledbetween the y die blocks, causes the aforesaid protuberances 24 to be extruded. Thus the protuberances canbeVVA size, shape and number of protuberances will obviously be dependent upon the purpose for which the screw is to be used. Some applications may require a lesser number, and others a greater i number of protuberances. Likewise, in some applications it may be advisable'to provide protub- --v'erances representingaxially extending ribs which are less in height than the ribs employed on screws intended to be usedfunder different con-r ditions. By having the locking ribs circumferentially spaced along the thread convolutions of the screw, as distinguished `from a continuous root portion of increaseddiameter, the turning ciably reduced.

'provides a'fluid seal. In other words, no leakage of fluid along the contacting thread surfaces will occur because the contacting surface areas of the 1 complementary thread convolutions in the work piece and screw are free from openings or voids through which leakage might otherwise take place. In instances where desired, the-screw may be hardened so as to meet the needs incident to its use. Obviously-it is preferable to have the thread convolutions of the screw harder than the thread convolutions of the work. This enables the protuberances or locking ribs of the screw to swage or knead surface areas of the thread convolutions of the work so as to provide a very effective lock and seal.

While for purposes of illustration, certain structural embodiments have been disclosed herein, it will be apparent that other changes and modifications may be made without departing from the spirit and scope of the appended claims.

The invention is hereby claimed as follows:

1. A self-locking and sealingv screw including a shank having a threaded locking section and a threaded leading section at the entering end thereof, and a plurality of circumferentially spaced integral protuberances projecting radially beyondthe normal thread periphery, including root portions interconnecting adjacent thread convolutions of the locking section at the root thereof, said protuberances extending radially beyond the normal root diameter of the screw sufficiently to lockingly inpinge the crown portions of complementary thread convolutions, said protuberances also including portions of limited and of substantially uniform cross section extending continuously from each of said root portions ,across at least the under surface of said thread convolutions into superimposing relation with respect to the crown thereof, said protuberances serving to prevent helical leakage along the thread surfaces.

2. A self-locking and sealing screw according to claim 1 wherein the integral protuberances include portions of limited cross section extending continuously from each of the root portions across both the upper and under surfaces of each thread convolution, the protuberances traversing said upper thread surface being sufficiently small to permit the thread surface positioned intermediate adjacent protuberances to impinge a complementary thread surface in the work when the screw is tightened therein.

RUDOLF K. F. BAUMLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

